1. Field Of The Invention
The present invention relates to a refrigerant compressor, and more particularly, to a wobble plate type compressor with a variable displacement mechanism suitable for use in an automotive air conditioning system.
2. Description Of The Prior Art
The use of a wobble plate type compressor with a variable displacement mechanism in an automotive air conditioning system is well known. The compressor includes a drive shaft with an inclined plate attached thereto, and a wobble plate located adjacent the inclined plate. The wobble plate is attached by connecting rods to pistons located in respective cylinders. Rotating motion of the drive shaft and inclined plate is converted into nutating motion of the wobble plate, reciprocating the pistons in the cylinders. The variable displacement mechanism controls the pressure in the crank chamber in accordance with external operating conditions to vary the inclination angle of the inclined plate. Accordingly, the stroke length of the pistons is varied in accordance with the change in angle of the inclined plate to change the compression ratio of the compressor.
If the compressor described above is used in an automotive air conditioning system, it is not necessary to control the air temperature by clutch cycling. Therefore, torque shock caused by clutch cycling is prevented. However, at the time when the main switch of the air conditioning system is turned on, it is initially necessary to turn the clutch on and off, thereby producing torque shock.
In light of the above problem, a coil spring is used to reduce the angle of the inclined plate with respect to the drive shaft when the main switch is off in order to reduce torque shock. However, when the clutch is turned on by the main switch, the suction pressure in the compressor becomes very large, and in the prior art, the pressure difference between the crank chamber and the suction chamber is almost equalized, thereby lowering the crank chamber pressure. Accordingly, a moment acs on the inclined plate so that its angle with respect to a plane perpendicular to the longitudinal axis of the drive shaft is at its greatest, producing a high compression capacity. This large compressor capacity occurs for an instant when the air conditioning system is turned on, producing an extremely large torque shock.